wasmtime / issue #10361 Cranelift: new assembler panics i... · git-wasmtime

Wasmtime GitHub notifications bot (Mar 10 2025 at 09:27):

With the following test-case

test compile
target x86_64

function %f0(i32, i32) -> i32 {
block0(v0: i32, v1: i32):
  v2 = band.i32 v0, v1
  return v2
}

when running the following command

$ RUST_BACKTRACE=1 RUST_LOG=trace cargo run -p cranelift-tools -- test ./test.clif

I get a panic like so:

 TRACE cranelift_codegen::machinst::lower      > lowering: inst inst0: v2 = band.i32 v0, v1
[ ... ]

thread 'worker #2' panicked at cranelift/codegen/src/isa/x64/inst/external.rs:95:9:
internal error: entered unreachable code
stack backtrace:
[ ... ]
   3: cranelift_codegen::isa::x64::inst::external::enc_gpr
             at ./cranelift/codegen/src/isa/x64/inst/external.rs:95:9
   4: <cranelift_codegen::isa::x64::inst::external::PairedGpr as cranelift_assembler_x64::api::AsReg>::enc
             at ./cranelift/codegen/src/isa/x64/inst/external.rs:35:20
   5: cranelift_assembler_x64::reg::Gpr<R>::enc
             at ./cranelift/assembler-x64/src/reg.rs:27:19
   6: cranelift_assembler_x64::reg::Gpr<R>::to_string
             at ./cranelift/assembler-x64/src/reg.rs:34:24
   7: <cranelift_assembler_x64::inst::andl_rm<R> as core::fmt::Display>::fmt
             at ./target/debug/build/cranelift-assembler-x64-0a4a19fac84309b6/out/assembler.rs:4336:19
[ ... ]
  22: cranelift_codegen::isa::x64::inst::<impl cranelift_codegen::machinst::reg::PrettyPrint for cranelift_codegen::isa::x64::lower::isle::generated_code::MInst>::pretty_print
             at ./cranelift/codegen/src/isa/x64/inst/mod.rs:1983:17
  23: cranelift_codegen::isa::x64::inst::<impl cranelift_codegen::machinst::MachInstEmit for cranelift_codegen::isa::x64::lower::isle::generated_code::MInst>::pretty_print_inst
             at ./cranelift/codegen/src/isa/x64/inst/mod.rs:2967:9
  24: cranelift_codegen::isa::x64::inst::<impl core::fmt::Debug for cranelift_codegen::isa::x64::lower::isle::generated_code::MInst>::fmt
             at ./cranelift/codegen/src/isa/x64/inst/mod.rs:1991:27
[ ... ]
  39: cranelift_codegen::machinst::lower::Lower<I>::emit
             at ./cranelift/codegen/src/lib.rs:103:13

Basically, it seems that the new assembler generates a Debug impl that only works post-regalloc, but we have trace-log messages that print instructions pre-regalloc; we need to handle this as well somehow. Perhaps we can make AsReg::enc() return an Option<u8> and use the underlying Debug (AsReg requires Debug) if the plugged-in register value does not have a hardware encoding (as a vreg won't)?

cc @abrown

Wasmtime GitHub notifications bot (Mar 11 2025 at 04:28):

abrown assigned abrown to issue #10361.

Wasmtime GitHub notifications bot (Mar 14 2025 at 15:10):